Vasodilatation produced by orientin and its mechanism study

Area of Science:

• Pharmacology
• Cardiovascular Research
• Natural Product Chemistry

Background:

• Orientin is a flavonoid isolated from bamboo leaves (Phyllostachys nigra).
• Vascular activity of natural compounds is of significant interest for therapeutic development.

Purpose of the Study:

• To investigate the vascular activity and elucidate the mechanism of action of Orientin.
• To determine the effect of Orientin on isolated rabbit thoracic aortic rings.

Main Methods:

• Isolated thoracic aortic rings from New Zealand rabbits were used to assess vasorelaxant effects.
• Concentration-response curves were generated for phenylephrine, norepinephrine, CaCl2, and KCl.
• The involvement of nitric oxide (NO) synthase, cyclooxygenase, K+ channels, and beta-receptors was examined using specific inhibitors.
• Levels of cyclic guanosine 3,5-cyclic monophosphate (cGMP) and adenosine-3',5'-cyclic phosphoric acid (cAMP) were measured.

Main Results:

• Orientin demonstrated significant vasorelaxant activity in endothelium-intact and endothelium-removed aortic rings.
• The vasorelaxant effect was dependent on the nitric oxide (NO)-cyclic guanosine 3,5-cyclic monophosphate (cGMP) pathway.
• Orientin inhibited vasoconstriction induced by norepinephrine, CaCl2, and KCl in a non-competitive manner.
• It was found to stimulate NO production and increase cGMP levels, without affecting cAMP.

Conclusions:

• Orientin relaxes thoracic aortic rings primarily through the nitric oxide-cGMP pathway.
• It inhibits vascular smooth muscle contraction by affecting receptor-operating and voltage-dependent Ca2+ channels.
• The study highlights Orientin's potential as a vasodilator, with implications for cardiovascular health.